---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 01/23/13: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:30 AM - LED landing light filter experiment (Robert L. Nuckolls, III) 2. 11:56 AM - Re: LED landing light filter experiment (James Kilford) 3. 12:25 PM - Re: LED landing light filter experiment (Sacha) 4. 03:09 PM - Re: LED landing light filter experiment (Robert L. Nuckolls, III) 5. 03:09 PM - Re: LED landing light filter experiment (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 11:30:13 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: LED landing light filter experiment A reader sent me a pair of high intensity LED fixtures after he discovered that they generated an unacceptable radio noise level. http://tinyurl.com/aytljbg I jury-rigged a filter from components I use on the BuckPuk supplies and mounted it to the back of the fixture on short leads. Emacs! The reduction of noise at 130 MHz is pronounced. I estimate 30 dB or better. Unfortunately, I've misplaced my set of precision attenuators so I'm unable to make a quantitative A vs. B comparison for effectiveness of the filter. Fortunately, they're cheap. I've ordered some that should be in early next week. I can put some real numbers on the experiment then. The goal is to head off the noise effects at the source. Wiring to the airplane will be ordinary, off-the-spool unshielded wire. When I'm ready to send these back to try on his airplane, I'll try them out on my '87 GMC truck to see how they compare with the stock headlights. Watch this space. Bob . . . ________________________________ Message 2 _____________________________________ Time: 11:56:51 AM PST US Subject: Re: AeroElectric-List: LED landing light filter experiment From: James Kilford Nice work Bob. Do you mind me asking... what is about these LED lights that makes them so noisy? In my head, LEDs are completely inert and therefore wouldn't create any interference. On 23 January 2013 19:28, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > A reader sent me a pair of high intensity LED fixtures after he > discovered that they generated an unacceptable radio noise level. > > http://tinyurl.com/aytljbg > > I jury-rigged a filter from components I use on the BuckPuk supplies > and mounted it to the back of the fixture on short leads. > > [image: Emacs!] > > > The reduction of noise at 130 MHz is pronounced. I estimate > 30 dB or better. Unfortunately, I've misplaced my set of > precision attenuators so I'm unable to make a quantitative > A vs. B comparison for effectiveness of the filter. > > Fortunately, they're cheap. I've ordered some that should be > in early next week. I can put some real numbers on the > experiment then. > > The goal is to head off the noise effects at the source. Wiring > to the airplane will be ordinary, off-the-spool unshielded wire. > When I'm ready to send these back to try on his airplane, I'll > try them out on my '87 GMC truck to see how they compare with the stock > headlights. > > Watch this space. > > ** > > ** Bob . . . > ________________________________ Message 3 _____________________________________ Time: 12:25:27 PM PST US Subject: Re: AeroElectric-List: LED landing light filter experiment From: Sacha Hi Bob, If you get satisfactory results from this, I for one would be very intereste d. Sacha On 23/gen/2013, at 19:28, "Robert L. Nuckolls, III" wrote: > A reader sent me a pair of high intensity LED fixtures after he > discovered that they generated an unacceptable radio noise level. > > http://tinyurl.com/aytljbg > > I jury-rigged a filter from components I use on the BuckPuk supplies > and mounted it to the back of the fixture on short leads. > > <9bf4435.jpg> > > > The reduction of noise at 130 MHz is pronounced. I estimate > 30 dB or better. Unfortunately, I've misplaced my set of > precision attenuators so I'm unable to make a quantitative > A vs. B comparison for effectiveness of the filter. > > Fortunately, they're cheap. I've ordered some that should be > in early next week. I can put some real numbers on the > experiment then. > > The goal is to head off the noise effects at the source. Wiring > to the airplane will be ordinary, off-the-spool unshielded wire. > When I'm ready to send these back to try on his airplane, I'll > try them out on my '87 GMC truck to see how they compare with the stock > headlights. > > Watch this space. > > Bob . . . ________________________________ Message 4 _____________________________________ Time: 03:09:07 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: LED landing light filter experiment At 02:24 PM 1/23/2013, you wrote: >Hi Bob, >If you get satisfactory results from this, I for one would be very >interested. >Sacha > Whether or not this particular configuration is the dragon slayer remains to be seen . . . but the dragon will be slain. Bob . . . ________________________________ Message 5 _____________________________________ Time: 03:09:12 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: LED landing light filter experiment At 01:54 PM 1/23/2013, you wrote: >Nice work Bob. =C2 Do you mind me asking... what >is about these LED lights that makes them so >noisy? =C2 In my head, LEDs are completely inert >and therefore wouldn't create any interference. You are, of course, correct. The LEDs are very quiet. Not zero noise . . . the electrical activity in the light emitting junction is pretty frenetic. But the aperture (antenna area) is very tiny so it's hard to detect . . . much less a risk for a noise source. The problem is that LEDs are CURRENT operated devices. You're probably familiar with the ubiquitous resistor wired in series with an LED to SET the current flowing through the device. To light an red LED (typical voltage drop on the order of 2 volts) from a 14v bus, you have to pick a resistor that causes the desired LED current to flow (30 mA) with a DROP of 12 volts. This means that the series resistor dissipates 6 TIMES as much energy as the LED . . . but it's so small as to be insignificant. POWER LEDs will demand much larger current values. Consider this device http://tinyurl.com/a2sggv4 which is rated at 10 watts. Note that it's rated to operate at 3 amps so one would guess that the operating voltage is about 3.3 volts (typical for white). So, using a simple series resistor for 14 volt systems would dissipate 30 watts . . . NOT insignificant. The elegant solution demands a special kind of DC to DC converter. VARIABLE voltage input (say 10 to 16 volts) and CONSTANT current output (3 A). Now, we can hook perhaps 3 to 6 lamps in series (10 to 20 volt operation) but at a constant current. This bit of electronic magic is ALWAYS noisy. Your computer, tv, and countless other appliances have similar power supplies but they're generally qualified to FCC part 15 rules for expected but limited emissions. No so with LED lamp fixtures from Fuzzy Joe's Motorcycle shop . . . or 24xydiy.com either. We had some discussions here on the list about LED position lights wherein a number of builders using a particular DIY kit were experiencing radio noise from the LuxDrive power supplies recommended for the installation. This prompted development of the filtered version of the LuxDrive part which I've offered now for several years [] This board is the foundation for the experimental filter I crafted for the aforementioned experiment. This jeeped experiment may not be the ideal way to go for an on-purpose filter but then, the then, the boards are already fabricated and in stock. Our very own Eric Jones offers an LED based tail light http://tinyurl.com/b377jtv Which has enjoyed the benefits of creative tailoring to the task and generates no objectionable noises. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.